As we so often repeat, the slang term pit bull does not define a breed, but a type.   The slang term pit bull can describe countless medium- and large-breed dogs, their mixes and lookalikes. (Some have even confused Chihuahuas for pit bulls!)    

Does it not follow that if pit bull is a conglomeration of breeds, mixes, and lookalikes rather than an actual breed, that statistics on pit bulls would be incredibly skewed?   And because indeed statistics on so-called pit bulls are skewed, they are false and therefore meaningless and worthless.   Also, because pit bull or pit bull-terrier is not a breed, its usage in legislation has consistently been found to be unconstitutionally vague (in addition to breed-specific legislation having been found to be unconstitutional in and of itself).